The present invention relates to a method of obtaining bimaterial parts by moulding.
More particularly, it relates to parts which consist of a core of aluminium alloy inserted into a matrix of another aluminium alloy.
This particular structure is used for example for making up motor vehicle parts such as cylinder heads in order locally to modify their properties and to incorporate channels into aeronautical parts which are produced by moulding.
Indeed, it is known that such parts are, in use, subjected to localised and particular stresses, especially heat-related stresses, and that to avoid certain unfortunate repercussions on their behaviour, general practice is to resort to incorporate into the parts inserts having properties which respond more satisfactorily to these stresses than does the basic material.
However, it has been found that the production of these bimaterial parts posed problems, particularly with regard to the connection between the insert and the matrix.
Indeed, on the one hand, adhesion between the constituents of the parts is not always suitable and then inadequate mechanical or physical properties (such as heat conductivity for example) result; on the other hand, as moulding is performed with a metal in the molten state by filling a mould in which the insert has been placed, if the metal forming the insert has a melting temperature below or close to that of the moulding metal, this can cause a deformation of the insert prejudicial to the correct positioning of the insert.
That is why the Applicants, aware of the interest which bimaterial parts offer and of the problems which arise when producing such parts, have sought and found a solution which constitutes the substance of the present invention.